Abstract
Laser surface hardening is rapidly growing in industrial applications due to its high flexibility, accuracy, cleanness and energy efficiency. However, the experimental process optimization can be a tricky task due to the number of involved parameters, thus suggesting for alternative approaches such as reliable numerical simulations. Conventional laser hardening models compute the achieved hardness on the basis of microstructure predictions due to carbon diffusion during the process heat thermal cycle. Nevertheless, this approach is very time consuming and not allows to simulate real complex products during laser treatments. To overcome this limitation, a novel simplified approach for laser surface hardening modelling is presented and discussed. The basic assumption consists in neglecting the austenite homogenization due to the short time and the insufficient carbon diffusion during the heating phase of the process. In the present work, this assumption is experimentally verified through nano-hardness measurements on C45 carbon steel samples both laser and oven treated by means of atomic force microscopy (AFM) technique.
Highlights
Laser hardening is a surface process with some peculiar characteristics such as that it does not require a quenching medium and it can be more selective if compared to the classical treatments carried out in an oven or by induction hardening
The effective applicability of laser transformation hardening depends on two basic aspects that determine the most important challenges in the development of this manufacturing technology: an accurate determination and control of the thermal field occurring onto the workpiece and the optimization of the laser scanning strategy when the part surface is larger than the beam spot size and multiple tracks have to be carried out (Tani et al 2008)
The experimental set-up In the present work, the negligible austenite homogenization during laser hardening process has been experimentally verified through hardness measurements on C45 specimens laser and oven treated obtained by means of atomic force microscopy (AFM) technique
Summary
Laser hardening is a surface process with some peculiar characteristics such as that it does not require a quenching medium and it can be more selective if compared to the classical treatments carried out in an oven or by induction hardening. Concerning the first aspect, due to the fast heat cycle occurring when the laser beam irradiates the target material, the hysteresis in the austenization of the steel is very high and the actual transformation occurs at temperatures very near to the solidus one. This consideration leads to conclude that an inaccurate control of the surface temperature can determine the. On the basis of the abovementioned considerations, setting up an effective laser surface hardening treatment emerges to be a complex activity often involving a costly and time expensive trial-and-error approach
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